...And today, with President Bush urging Congress to create a new guest-worker program, his tale highlights some of the cautionary lessons that similar programs in the US and Europe hold.

Among them, experts say:

* Such programs are often set up with the needs of employers in mind - making workers vulnerable to exploitation.

* Even if guest workers aren't put officially on a path to permanent residency, many stay in the host nation for good.

* The creation of a new legal status for guest workers doesn't necessarily slow illegal immigration.

...Since World War II, "the Swiss tried it with the Italians and Spanish, the Germans tried it with the Turks, and the French with the Algerians," says Paul Heise, professor of economics at Lebanon Valley College in Annville, Pa. "Everywhere, it has been a disaster for both the welfare of the workers and the moral character of the employing country."

The biggest problem of all, some say, is that once workers and their families become established in a new country, they do not want to leave. "The main lesson of previous guest-worker programs in the US and across Europe is that there is nothing more permanent than a temporary worker," says Rosemary Jenks, of Numbers USA, which works to limit immigration. "History has yet to find an effective and humane way to make them go home."

Often, workers develop families and roots in their adopted countries but cannot become citizens and thus live a kind of second-class status...